1. Field of the Invention
The present invention relates to a field of application of nuclear technique, more particularly, to a non-destructive detecting device and method for human and object. In general, it relates to a scanning device and method for imaging with back-scatter radiation beam.
2. Description of the Related Art
In the field of non-destructive detection and human body detection, there are two types of imaging approaches with radiation rays: transmission imaging and back-scatter imaging. The principle of the back-scatter imaging is that the object is scanned by a radiation beam, and at the same time scattering signals scattered from the object to be scanned are received by a detector. During the subsequent data processing step, the scanning positions are correlated to the scattering signals one by one, and thereby obtaining the scattering image about the object to be scanned. The key component in the back-scatter imaging system is a flying spot scanning mechanism which collimates ray so as to carry out two-dimensional scanning.
In a flying spot scanning mechanism in the prior art, a rotatable shield body with a plurality of collimated holes is employed to perform an one dimensional scan (referred as a first dimensional scan) by rotating it within a ray scanning sector, and to perform another dimensional scan (referred as a second dimensional scan) by rotating or translating the ray scanning sector. As for the first dimensional scan, ray is scanned in a non-uniform velocity over a vertical plane of the object, the scanning line is accelerated at both leading and trailing ends when scanning. Further, the scanning spot is further longitudinally enlarged on the basis of the geometry deformation, so that the image has a longitudinally compressive deformation due to the change of the scanning speed in addition to the geometry deformation.
When performing the second dimensional scan through translating the ray scanning sector, it is necessary to translate a ray generator and the rotatable shield body. As a result, the construction and configuration of the scanning device become rather complicated. On the other hand, if ray scanning sector is rotated during scanning operation, it is required to overcome rotational inertia for rotating the shield body. Meanwhile, it imposes enormous impact and pressure on the driving device for rotating the shield body and a bearing structure for bearing the shield body when the rotation operation is carried out.
Another known flying spot scanning mechanism comprises a fixed shield plate located at front of a ray source and a rotatable shield body. The fixed shield plate is stationary with respect to the ray source, and the rotatable shield body is rotatable with respect to the fixed shield plate. The fixed shield plate is provided with a rectilinear slit while the rotatable shield body is provided with a spiral slit, respectively. Upon performing scanning through rotating the rotatable shield body, the rectilinear slit continually intersects with the spiral slit to generate collimated holes for scanning which always keep a predetermined shape with respect to the ray source, so that a sectional shape of the radiation beam passing through the collimated hole for scanning is kept to be constant.
In the above configuration, since the spiral slit is arranged on the rotatable shield body, it is easy to control the shape and size of the collimated hole for scanning. Meanwhile, it is necessary to further improve and enhance shielding of the radiation rays.
Furthermore, since the rotatable shield body is required to be precisely machined to have the spiral slit, which engenders problems and rigorous requirements on manufacturing the rotatable shield body.
Moreover, the rotatable shield body is required to rotate during the scanning, thereby giving rise to a problem that the weight and rotatable inertia of the scanning should be taken into accounts.
Accordingly, it is desirable to provide a novel scanning device for back-scatter imaging with the radiation beam, which can meet at least one aspect of the above requirements or demands.